Can loopcuts be made when Blender is in background with the "-b" option?
It's actually quite simple:
You can't use operators in background mode.

When Blender is in background mode or you use Blender as a Python module, then the context does not work as usual, because it doesn't exist. There has to be a 3D viewport etc. for the context to work but all of those things don't exist in background mode.

The solution is to use the internal functions of the operator you are trying to use. But if this operator does not use internal functions you are out of luck.

I got this info from a youtube video where the blender devs answered questions (at about 11 minutes in).